<!DOCTYPE HTML>
<html>
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <title>prompt</title>
    <script type="text/javascript">
        function rec(){
            var score; //score变量，用来存储用户输入的成绩值。
            score =  prompt("请输入你的分数");              ;
            if(score>=90)
            {
                document.write("你很棒!");
            }
            else if(score>=75)
            {
                document.write("不错吆!");
            }
            else if(score>=60)
            {
                document.write("要加油!");
            }
            else
            {
                document.write("要努力了!");
            }
        }
    </script>
</head>
<body>
<input name="button" type="button" onClick="rec()" value="点击我，对成绩做评价!" />
</body>
</html>